A new linear dynamic model of a six-spherical-prismatic-spherical (SPS) Stewart platform with the base excitation was formulated via Kane’s method. In order to satisfy the practical situation, the uncertainties of mass center location, stiffness and damping were concerned. Then a robust μ-synthesis controller was developed by applying D-K iteration to attenuate the base excitation. Comparisons were conducted by analyzing the responses of the open and closed loops in the frequency and time domain. Simulation results indicated that the proposed robust controller is of fine properties and good robustness, which laid a sound foundation of active micro-vibration control of a satellite.